Mumbai was the second largest emitter of SO2 in 2018: Study

Studies have found SO2, a colourless pollutant gas, contributes to deaths from air pollution as well as acidification of soil and surface waters.

mumbaiUpdated: Aug 20, 2019 02:57 IST

Badri Chatterjee

Mumbai

The largest source of SO2 emissions is the burning of fossil fuels such as coal, oil and gas.(HT image)

A new study found India was the largest emitter of sulphur dioxide (SO2) in 2018, with Mumbai as the second-most polluted megacity in the country. The study, published on Monday, was carried out by environmental activist group Greenpeace and used satellite data from National Aeronautics and Space Administration (NASA). However, authorities maintained SO2 levels were low and no cause for concern.

According to Greenpeace’s report titled Global SO2 Emission Hotspot Database, Chennai was the most polluted Indian megacity with 215 kilotons (kt) of SO2 emissions in 2018. For Mumbai, the second-most polluted megacity in India, the major source of SO2 emissions (42 kt in 2018) was Trombay with its power plant and oil refineries. Other coal power generation hubs in Maharashtra that showed up on the global SO2 map were Chandrapur, Koradi (near Nagpur), Nashik, Akola, Bhusawal (in Jalgaon) and Parli (in Beed).

Studies have found SO2, a colourless pollutant gas, contributes to deaths from air pollution as well as acidification of soil and surface waters. The largest source of SO2 emissions is the burning of fossil fuels such as coal, oil and gas.

“Mumbai showing up as the second-most polluted megacity is a grim reminder that air pollution is a national health crisis not just restricted to Delhi-NCR,” said Sunil Dahiya, campaigner, Global Air Pollution unit, Greenpeace.

The Maharashtra Pollution Control Board (MPCB) said measures like installing flue gas emission desulphurisation (FGD) systems were in place to tackle SO2 levels. “Industries located at Trombay are complying with Central Pollution Control Board standards and already have FGDs in place. So it is unclear where the SO2 is coming from,” said Sudhir Srivastava, chairman, MPCB. He said stricter norms have been enforced across major industries in Maharashtra since 2015 to reduce emissions.

The CPCB reiterated that the process of addressing SO2 emissions was underway. “For Mumbai, all sources, including industries, have been targeted under the city’s action plan,” said V Shukla, scientist in-charge of air quality management, CPCB. According to CPCB’s annual data, SO2 concentration in Mumbai remained below 20 microgram per cubic metre (µg/m3) from 2009-10 to 2018-19, against the safe limit of 50µg/m3. Similarly, all other major cities, apart from Kalyan, recorded levels below 30µg/m3.

However, Dahiya said Greenpeace’s study points to sources near Chembur and other spots that could lead to “a health emergency situation”. “It is crucial that the government takes up the clean air action plan implementation through stricter norms for all sectors,” said Dahiya.

Greenpeace’s study evoked mixed reactions from experts. “Satellite data is not reliable until on-ground verification is done. A five-year study by CPCB found negligible impact on receptors [citizens] for SO2 emissions. Also, this is the only pollutant well below the safe limit across India,” said D Saha, former additional director, CPCB.

Anumita Roy Chowdhury, executive director (research and advocacy), Centre for Science and Environment, said low SO2 levels may still be cause for concern. “In tropical conditions (as in India), this low SO2 level can be deceptive as we are not able to capture the cycle forming secondary particles contributing to overall air pollution. There is need for more studies,” she said.